Adding 20 teaspoons more of er than a recipe calls for?! need help ASAP?

I am making fruity pebble rice crispe treats the recipe calls for 6 cups of fruity pebbles, 10.5 ounce bag of marsh mellows and 4-6 teaspoons of er....For various reasons it is imperative that i add a half cup of er to the recipe, so my question to you is how it will affect the out come of my product.